A considerable number of releasable backhoe boom locks have been used that do not rely upon fluid pressure in the rams for locking a boom to a frame member and enabling the transport thereof in a positive retracted position. Examples of the prior art are shown in U.S. Pat. Nos. 3,811,582 issued to J. F. Shumaker, et al on May 21, 1974; 3,921,835 issued to D. C. Baker, et al on Nov. 25, 1975; 4,184,803 issued to R. D. Housman on Jan. 22, 1980; and 4,225,282 issued to W. A. Nordstrom, et al on Sept. 30, 1980. However, even though some of these devices have been at least partially successful they have had individual drawbacks.
The boom locks disclosed in aforementioned U.S. Pat. No. 3,811,582 require pivotal or guidable latching members that are resiliently biased toward one position by a separate spring. This unnecessarily adds complexity and cost, and lowers the degree of positive reliability required in the relatively harsh working environment of an earthworking vehicle. Moreover, there is no provision for the convenient adjustment of the distance between the latch and pin members to compensate for manufacturing tolerances or wear.
In aforementioned U.S. Pat. No. 3,921,835 a horizontally pivoted ring structure and cooperating spring biasing means is utilized to enable coupling of the ring structure over an upstanding pin and locking of the boom to a swing frame member. Hence, this construction exhibits generally the same deficiencies as discussed above with respect to Pat. No. 3,811,582.
Likewise, the boom locks of U.S. Pat. Nos. 4,184,803 and 4,225,282 are more complex and costly than desired, and are more easily subject to adjustment problems and possible malfunction because of the number of pivot pin joints, springs and attachment brackets which are required.
In view of the above, it would be advantageous to provide a less complex and yet reliable releasable lock for automatically locking a boom to a frame in response to pivotally retracting the boom to its transport position. Also, in addition to allowing the convenient manual release of the lock from the operator station, the boom lock should be easily longitudinally adjustable and be capable of ready incorporation on existing vehicles with a minimum of modification thereof.
The present invention is directed to overcoming one or more of the problems as set forth above.